Method of producing hydrocarbons from an oil shale formation containing halite

ABSTRACT

A method of producing hydrocarbons and optionally halite from a subterranean oil shale formation containing zone(s) of halite, by penetrating said formation with at least one borehole and leaching or dissolving the halite from the formation with a solvent fluid so as to form a cavern(s) and/or interconnected cavities, followed by fracturization and/or rubblization of the oil shale surrounding the caverns or cavities, and thereafter injecting into the fracturized and/or rubblized zones, a pyrolyzing fluid to effect insitu hydrocarbon recovery therefrom.

United States Patent 1 [111 3,753,594

Beard Aug. 21, 1973 METHOD OF PRODUCING 3,510,167 5/1970 Carmody 299/4HYDROCARBONS FROM AN 01L SHALE 3,502,372 3/1970 Prats 299/5 FORMATIONCONTAINING HALITE Thomas N. Beard, Denver, Colo.

Assignee: Shell Oil Company, New York, N.Y.

Filed: Sept. 24, 1970 Appl. No; 75,037

Related US. Application Data Continuation-impart of Ser. No. 770,964,Oct. 28, 1968, abandoned.

Inventor:

US. Cl. 299/4, 166/271 Int. Cl E2lb 43/28 Field of Search 299/4, 5;166/259,

References Cited UNITED STATES PATENTS 12/1969 Prats 166/251 PrimaryExaminer-Robert L. Wolfe Attorney-George G. Pritzker and Harold L.Denkler ABSTRACT A method of producing hydrocarbons and optionallyhalite from a subterranean oil shale formation containing zone(s) ofhalite, by penetrating said formation with at least one borehole andleaching or dissolving the halite from the formation with a solventfluid so as to form a cavern(s) and/or interconnected cavities, followedby fracturization and/or rubblization of the oil shale surrounding thecaverns or cavities, and thereafter injecting into the fracturizedand/or rubblized zones, a pyrolyzing fluid to effect insitu hydrocarbonrecovery therefrom.

5 Claims, 2 Drawing Figures "E IL-ul: -1,

Patented Aug. 21, 1973 lOb INVENTOR:

N. BEARD 1 M HIS AG NT FIG.2

METHOD OF PRODUCING HYDROCARBONS FROM AN OIL SHALE FORMATION CONTAININGI-IALITE CROSS-REFERENCE TO RELATED APPLICATIONS This application is acontinuation-in-part of copending application Ser. No. 770,964, filedOct. 28, 1968 and now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to the recovery of hydrocarbons and optionally halite fromunderground oil shale formations containing halite deposits. Moreparticularly, it relates to hydrocarbon recovery by in-situ thermalfluid extraction of oil shale within a fracturized and/or rubblizedportion of a subterranean oil shale formation in and around a cavernand/or interconnected cavities formed by leaching or dissolving, e.g.,solution mining of the halite therefrom.

2. Description of the Prior Art Large deposits of oil in the form of oilshale are found in various sections of the United States, particularlyin Colorado and surrounding states and Canada. Various methods ofrecovery of oil from these shale deposits have been proposed and theprincipal difficulty with these methods is their high cost which rendersthe recovered oil too expensive to compete with petroleum crudesrecovered by more conventional methods. Mining the oil shale andremoving the oil therefrom by above-ground retorting in furnacespresents a disposal and pollution problem and also such processes arealso generally commercially uneconomical. In-situ retorting to convertthe oil shale to recover the oil contained therein is made difficultbecause of the non-permeable nature of the oil shale. The art disclosesvarious means of improving oil recovery of oil from oil shale such asdescribed in U.S. Pat. Nos. 3,400,762 or 3,437,378 or 3,478,825 andparticularly various means of increasing permeability of oil shaleformations as described in U.S. Pat. Nos. 3,273,649 or 3,481,398 or3,502,372, or copending application Ser. No. 839,350, filed July 7,1969. Although these references are directed to an advancement of theart, the basic technique for recovering oil from oil shale stillrequires rubblization techniques such as by means of explosive devices,e.g., nuclear energy which is expensive, difficult to control andpresents a radioactive contamination problem all of which are veryundesirable.

OBJECTS OF THE INVENTION It is an object of this invention to provide animproved method for recovering hydrocarbons from a halite containing oilshale formation by leaching or dissolving the halite such as by solutionmining so as to form a cavern and/or interconnected cavities within theoil shale formation.

It is a further object of the invention to effect rubblization and/orfracturization of the halite leached oil shale formation surrounding thecavern and/or cavities so as to form a permeable zone thereby enhancinginsitu thermal fluid extraction (pyrolysis) of hydrocarbons therefrom.

Still another object of this invention is to effect insitu pyrolysis toproduce hydrocarbons from oil shale subjected to leaching, rubblizationand fracturization as indicated in the previous two paragraphs, andsubsequently recovering the hydrocarbons by suitable means.

Still another object of the present invention is to recover watersolubleminerals from a rich halite containing oil shale formation that may beremoved during the leaching and/or solution mining, rubblization and/orfracturization, and/or pyrolysis processes.

Still another object of the present invention is to sequentially and/orsimultaneously recover halite and hydrocarbons from halite containingoil shale formations that may be removed during the leaching and/orsolution mining, rubblization and/or fracturization and/or pyrolysisprocesses.

Other objects of the invention will be apparent from the followingdescription.-

SUMMARY OF THE INVENTION The present invention is directed to recoveryof hydrocarbons and optionally halite from a halite containing oil shaleformation by the following steps: (1) subjecting a rich halite zone(s)of an oil shale formation to a leaching, dissolving or solution miningprocess so as to remove the halite, thereby creating porosity to allowfor thermal expansion of the oil shale and establish communicationthrough the treated zone(s), (2) effecting in said leached zone(s)rubblization and/or fracturization so as to form zone(s) of rubblizedand/or fractured oil shale with large surface area for more efficientheat treatment by in-situ thermal fluid extraction (pyrolysis) and (3)injecting into the rubblized and/or fracturized oil shale zone(s) apyrolyzing fluid to effect hydrocarbon recovery.

The halite and hydrocarbons may be recovered sequentially orsimultaneously and if the latter, the two products can be separated bysuitable means such as settling or solvent extraction above ground. Theoil shale formation may contain more than one zone of rich halite whichzones may be separated by impermeable oil shale layers of several feetto several hundred feet and each of these halite layers or zones can beleached or dissolved or solution mined in accordance with the process ofthe present invention.

The first or initial step should be so designed to create a cavern orinterconnecting cavities in the halite bed(s) or zone(s) by dissolving,leaching or solution mining techniques through at least one boreholepenetrating said formation. Leaching can be effected by cold or hotaqueous solutions either at atmospheric or elevated pressures. When hotsolutions are used such as hot water and/or steam, more rapiddissolution is effected to produce void spaces in the oil shaleformation thereby providing and enhancing well communication, space forthermal expansion of the shale, and greater surface contact withsubsequent pyrolyzing fluid.

If necessary, fracturing the formation either before or after leachingby conventional means such as hydrofracturing, explosive means, nuclearmeans, etc., may be desirable. The leaching solutions can containchemical agents to enhance dissolution of the minerals.

Leaching or solution mining of the halite can be accomplished by asuitable solution mining technique such as described in U.S. Pat. Nos.2,618,475; 3,387,888; 3,393,013; 3,402,966; 3,236,564; 3,510,167 orCanadian patents 832,828 or 832,276 or as described in copendingapplication Ser. No. 2,765, filed Jan. 14, 1970. Spalling and rubblingcan be accomplished by the method described in US. Pat. No. 3,478,825 orby other means such as by hydraulic explosive, nuclear, electricalmeans. Preferably rubblization is accomplished by hot fluid circulationthrough two caverns causing the two walls to spall and fracture. ln-situthermal recovery of oil can be effected by a pyrolyzing fluid such assteam and/or hot water or solvent extraction means.

The circulation of a pyrolyzing fluid not only effects oil recovery butalso effects thermal rubblirig and/or fracturization. Also, if thepyrolyzing fluid such as steam is used to extract and recover oil, morehalite may be dissolved perpetuating the process.

The term pyrolyzing fluid is used to refer to a liquid or gas which bymeans of thermal, chemical and/or solvent action, interacts with thekerogen components of an oil shale to produce and entrain hydrocarbonsuch as oil. Such a fluid can be comprised of hot fluids such as hotwater or steam or mixtures of hot water and steam, hot hydrocarbonsand/or mixtures of such fluids with chemicals such as acids, e.g., I-ICland/or organic solvents, benzene, toluene, cumene, phenol, etc. Thekerogen pyrolyzing fluid can be heated by surface or borehole-locatedheating devices. The kerogenpyrolyzing fluid can advantageously compriseor contain a solvent for the halite, such as a steam condensate, havingatemperature such as of at least lOF, such as from about 450F to aboveabout l,500F and preferably from about 550F to 1,000F. Where thekerogen-pyrolyzing fluid contains or forms aqueous components, itscirculation through the treated oil shale formation can enlarge thecavern, by solution mining the soluble minerals, while shale oil isbeing produced. Also, simultaneously or sequentially, pyrolyzing and oilextracting fluids can be used such as steam followed by a solvent suchas phenol or benzene.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view,partly diagrammatic, of an embodiment of the invention showing aformation penetration by more than one well; and

FIG. 2 is a sectional view of an embodiment of the invention, theformation being penetrated by a single well.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. I of thedrawing, a plurality of well boreholes are shown penetrating into asubterranean oil shale formation 9 which contain rich zones of halite10, 10a and 10b. An injection well borehole 11 is shown extending intooil shale formation 9 and rich halite zone(s) 10 or multizones such as100 and 10b that are located within the oil shale formation 9 and arealso encountered by well borehole 12. Well boreholes 11 and 12 areillustrated by having casings 13 through 14, respectively, cemented inplace in their respective boreholes by suitable sealants 15 through 16,respectively. Although only a single injection well borehole 1 1 and asingle production well borehole 12 have been illustrated, obviouslyvarious combinations of one or more injection and production wells maybe provided by one skilled in the art.

Fluid communication between well boreholes l1 and 12 (FIG. 1) and thezones rich in halite therebetween may be established by solution mininga cavern or cavities 23, through the soluble mineral zones.Communication can be enhanced by means of conventional hydraulic,electric, and/or explosive fracturing tech niques, all well known in theart. Where, for example, subterranean stresses in and around solublemineral zones 10, 10a, and 10b are conducive to the formation ofhorizontal fractures, the fluid communication between well boreholes 11and I2 and the halite can be established by a conventional hydraulicfracturing technique. Referring to FIG. 1, after fluid communication hasbeen established between a pair of wells, aqueous leaching or solutionmining liquid is injected through tubing 17 down well borehole 11, outthrough perforations l8 opposite any or all of the soluble beds throughthe bed 10, 10a and/or 10b up borehole 12 through tubing via perforation19 creating a leached cavern 23. The aqueous liquid may comprise waterand/or steam or aqueous solutions of acid or acidforming materials andis circulated at pressures either above or below the over-burdenpressure. The circulating aqueous liquid dissolves the halite which isrecovered from the fluid flowing out of well borehole 12, for example,by conventional evaporation and/or precipitation procedures.

Fluid communication can also be established in one borehole between atleast two spaced portions of the well borehole and the halite (as forexample, in FIG. 2 communication is through the tubing strings, the endsof which are open to the halite and some distance apart). Thus, a singlewell may be utilized by a dual zone completion arrangement as shown inFIG. 2 such that fluids can be injected at one point of the well andproduced from another point of the same well. In FIG. 2, the wellbore is26, the casing is 27, the sealant is 28, within the casing are theinjection tubing string 29 and production tubing string 30, the borehole26 penetrates oil 0shale formation 9 with halite zone(s) 10 ormultizones 10a and 10b.

Fracturing pressures are generated within the oil shale formation 9while lower pressures are maintained within the cavern 23 which isformed within oil shale formation 9 by the removal of the halite. Thesepressures are preferably generated by merely circulating hot fluidthrough cavern 23. As the walls of the cavern(s) 23 (23a FIG. 2) areheated kerogen is pyrolyzed within the cavern walls and the pressures ofthe pyrolysis products increase until portions of the walls are spalledinto the cavern 23 creating a rubblized zone 24 (240 FIG. 2) andsurrounding fracture area 25 (25a FIG. 2).

Alternatively, fracturization and/or rubblization can be accomplished byconventional means such as hydraulic, explosive means and the like. Toprovide additional void space, if necessary, further leaching can beconducted.

Finally, a kerogen-pyrolyzing fluid such as steam is circulated fromwell borehole 11 (FIG. 1) through the rubblized zone 24 and fracturedzone 25 of oil shale formation 9 and out of well borehole l2.Hydrocarbon materials are then recovered from the heated fluidcirculating out of well borehole 12 by means well known in the art.Removal of hydrocarbons from the oil shale provides additional voidspace enlarging the original rubblized zone, perpetrating the process.Similar techniques can be applied to single wells as shown in FIG. 2.

Conventional equipment and techniques, such as heating means, pumpingmeans, separators and heat exchangers may be used for pressurizing,heating, injecting, producing and separating components of the heatedfluid circulating through the oil shale formation 9. The production ofthe fluid may be aided by downhole pumping means, not shown, orrestricted to the extent necessary to maintain the selected pressurewithin the oil shale formation 9.

The fluid circulated through rubblized zone 24 and fractured zone 25(FIG. 1) to recover oil shale from oil shale formation 9 may compriseany heated gas, liquid or steam. Oil shale reactive properties may alsobe imparted to the circulating fluid as discussed hereinabove.

Where the oil shale formation contains a zone rich in halite in whichzone the halite occur in the form of adjacent but discrete nodules orlenses 31, or the like, the present process is applied as describedabove. In this situation, the caverns comprise a network of relativelysmall cavities that are interconnected by fractures.

It is understood that various changes in the detailed described toexplain the invention can be made by persons skilled in the art withinthe scope of the invention as expressed in the appended claims.

I claim as my invention:

1. A method of producing hydrocarbons from a subterranean oil shaleformation having halite containing zones therein comprising the stepsof:

a. penetrating a well borehole into the halite zone of the oil shaleformation;

b. injecting water down the well borehole and into the halite containingzone to leach and withdraw halite thereby creating voids and cavities inthe formation;

c. injecting a non-combustible pyrolyzing fluid into the leached voidsand cavities to effect extraction of hydrocarbons from the oil shale;and

d. recovering the hydrocarbons from treatment (0) above ground.

2. The method of claim 1 wherein the pyrolyzing fluid comprises steamhaving a temperature sufficient to thermally fracture oil shale adjacentthe leached voids and cavities.

3. The method of claim 1 wherein at least two wells penetrate theformation one of which functions as an injection well and one as aproduction well.

4. The method of claim 2 wherein the halite is removed by steam usedalso to effect hydrocarbon recovcry.

5. The method of claim 4 wherein the halite and hydrocarbon arerecovered simultaneously.

2. The method of claim 1 wherein the pyrolyzing fluid comprises steamhaving a temperature sufficient to thermally fracture oil shale adjacentthe leached voids and cavities.
 3. The method of claim 1 wherein atleast two wells penetrate the formation one of which functions as aninjection well and one as a production well.
 4. The method of claim 2wherein the halite is removed by steam used also to effect hydrocarbonrecovery.
 5. The method of claim 4 wherein the halite and hydrocarbonare recovered simultaneously.